Add read with timeout to uart driver

Adds a new uart:read/2 that takes a timeout parameter for reads. If no data is received during the
timeout period `timeout` is returned, and the listener is removed allowing for another read without
getting the `{error, ealready}` error tuple.

Closes #1446

Signed-off-by: Winford <[email protected]>

src/platforms/esp32/components/avm_builtins/uart_driver.c

@@ -101,6 +101,7 @@ static const AtomStringIntPair cmd_table[] = {
     { ATOM_STR("\x4", "read"), UARTReadCmd },
     { ATOM_STR("\x5", "write"), UARTWriteCmd },
     { ATOM_STR("\x5", "close"), UARTCloseCmd },
+    { ATOM_STR("\xB", "cancel_read"), UARTCancelCmd },
     SELECT_INT_DEFAULT(UARTInvalidCmd)
 };
 
@@ -384,6 +385,23 @@ static void uart_driver_do_read(Context *ctx, GenMessage gen_message)
     }
 }
 
+static void uart_driver_do_cancel_read(Context *ctx, GenMessage gen_message)
+{
+    struct UARTData *uart_data = ctx->platform_data;
+
+    safe_update_reader_data(uart_data, NO_READER, NO_REF);
+
+    term pid = gen_message.pid;
+    term ref = gen_message.ref;
+
+    if (UNLIKELY(memory_ensure_free_with_roots(ctx, TUPLE_SIZE(2), 1, &ref, MEMORY_CAN_SHRINK) != MEMORY_GC_OK)) {
+        ESP_LOGE(TAG, "[uart_driver_do_read] Failed to allocate space for return value");
+        globalcontext_send_message(ctx->global, term_to_local_process_id(pid), OUT_OF_MEMORY_ATOM);
+    }
+
+    port_send_reply(ctx, pid, ref, OK_ATOM);
+}
+
 static void uart_driver_do_write(Context *ctx, GenMessage gen_message)
 {
     GlobalContext *glb = ctx->global;
@@ -523,6 +541,11 @@ static NativeHandlerResult uart_driver_consume_mailbox(Context *ctx)
                 is_closed = true;
                 break;
 
+            case UARTCancelCmd:
+                TRACE("cancel_read\n");
+                uart_driver_do_cancel_read(ctx, gen_message);
+                break;
+
             default:
                 TRACE("uart: error: unrecognized command.\n");
         }